JPH0481805A - Optical waveguide and its manufacturing method - Google Patents

Abstract

PURPOSE:To suppress the stray light propagating in a clad to a lower level by forming a base material having groove parts of an opaque material, then applying a light transparent material having a low refractive index thereon to form a clad layer, packing a light transparent material having a high refractive index on the groove parts to form core parts and forming a clad coating layer consisting of a light transparent material having a low refractive index thereon. CONSTITUTION:The base material 11 having the groove part 12 is produced. The material of the base material 11 is opaque to an incident light beam. The light transparent material having the low refractive index is applied by a spin coating method on the surface having the groove parts 12 of the base material 11 and further, the coating is irradiated with UV rays under rotation to completely cure the light transparent material and to form the clad layer 13. The light transparent material having the high refractive index is then filled into the groove parts of the base material 11 from one end thereof by utilizing capillarity. After the light transparent material is filled therein, the material is irradiated with UV rays and is thereby cured to form the core parts 14. Finally, the light transparent material having the low refractive index is applied on the core part 14 forming surface of the base material 11 and is cured by irradiation with the UV rays, by which the clad coating layer 15 is formed. The optical waveguide is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical waveguide used as an optical transmission path for optical writing devices, optical reading devices, optical integrated circuits, etc., and a method for manufacturing the same.

[Prior Art] An optical waveguide consists of a core portion through which light passes and a cladding portion surrounding the outside of the core portion.The light propagates through repeated reflections within the core portion, and is particularly cylindrical or linear and has a central portion. An optical fiber has a core and a circular cladding on the outside.

Conventionally, various manufacturing methods using photolithography have been proposed as methods for manufacturing optical waveguides. For example, there is a selective polymerization method shown in FIGS. 2(a) to 2(d). (refractive index 1.59), acrylic monomer 32 (refractive index 1.48 to 1.4 after polymerization)
9) to form a film-like solution. Figure 2 (
a)), then a photomask 3 with a waveguide pattern drawn on it
When 4 is placed in close contact with the film 33 prepared in FIG. 2(a) and irradiated with ultraviolet rays 35, the acrylic monomer 32 in the irradiated area polymerizes to form polycarbonate 31 and copolymer 36 (refractive index 1, 53). is formed (Fig. 2(b)
). Next, by vacuum drying the film 33, the acrylic monomer 32 remaining in the unirradiated area is removed from the film 33.
When removed from 3, only polycarbonate remains, and the polycarbonate part 37 has a higher refractive index than the copolymer part 36. The polycarbonate part 37 becomes the optical waveguide part, that is, the core part, and the copolymer part 36 becomes the clad part (second figure(
C)). Thereafter, a film-like plastic optical waveguide 39 was manufactured by covering both sides of the film 33 with the same low refractive index material 38 as the cladding part (Fig. 2(d)
)).

Generally, when a light beam is made to enter an optical waveguide, it is difficult to make the light beam enter only the core portion, and the light beam also enters the cladding portion. The light beam incident on the cladding portion propagates within the optical waveguide, spreads over the whole at the specific radiation end, and is emitted. Such light is called stray light and is sensed as a signal along with the light beam emitted from the core. Stray light can be suppressed to a negligible level by making the width of the cladding part sufficiently smaller than that of the core part.

[Problems to be Solved by the Invention] However, in the optical waveguide manufactured by the above method, the cladding part becomes approximately trapezoidal due to scattering of ultraviolet rays during exposure (FIG. 2(b)), and the cladding part becomes smaller than the core part. Since it is impossible to make the cladding portion sufficiently small, stray light cannot be suppressed to a negligible level and is sensed as a signal.

For example, when such an optical waveguide is used in a writing device, a light beam as information is emitted from the core,
The ratio of the light beam as noise caused by stray light, that is, the signal-to-noise ratio decreased, making it impossible to write with high contrast.

The present invention aims to solve the above-mentioned problems, and its purpose is to provide an optical waveguide and a method for manufacturing the same in which stray light propagating within the cladding can be suppressed to a negligible level.

Means for Solving the Problem] The present invention provides a base material made of an opaque material having a groove, a cladding layer made of a light-transmitting material with a low refractive index formed on a surface of the base material having the groove, and a cladding layer made of a transparent material having a low refractive index, and It consists of a core part made of a translucent material with a high refractive index filled in the groove of the layer, and a cladding layer made of a translucent material with a low refractive index which covers the cladding layer and the upper part of the core part. An optical waveguide characterized by
In the method for manufacturing an optical waveguide, a base material having a groove is formed of an opaque material, and a cladding layer is formed by applying a light-transmitting material with a low refractive index to the surface of the groove of the base material. Relating to a method for manufacturing an optical waveguide, the method comprising filling a groove with a translucent material having a high refractive index to form a core portion, and forming a cladding layer thereon using a translucent material having a low refractive index. .

[Function] The width of the cladding part is sufficiently smaller than the width of the core part.
Moreover, since the core parts are partitioned with an opaque material, the light beam incident on the cladding part can be suppressed to a negligible level, and therefore the stray light propagating through the cladding part can also be suppressed to a negligible level, which can be detected as a signal. Stray light can be minimized.

[Example] Next, the present invention will be explained based on an example. Figure 1(a)
-(d) show the steps of forming an optical waveguide by the optical waveguide manufacturing method of the present invention. First, Figure 1(a)
A base material 11 having grooves 12 is prepared as shown in FIG. The base material 11 may be made of any material as long as it is opaque to the incident light beam. Next, a light-transmitting material with a low refractive index is applied to the surface of the base material 11 on which the groove portion 12 is located. As the transparent material, for example, an ultraviolet curing resin (trade name: Aronix M-310, manufactured by Toagosei Chemical Industry Co., Ltd.) is used. Further, as a method for applying the light-transmitting material, a spin coating method is preferable, and a thin and uniform coating can be obtained by this method. In addition, the thickness of the coating film is such that the light beam propagating within the core does not seep out, and spin coating is performed at 8000 rpm for 30 seconds.
The transparent material is completely cured by irradiating ultraviolet rays while rotating for another minute, thereby forming a cladding layer 13 as shown in FIG. 1(b). When ultraviolet rays are irradiated after the rotation is stopped, the cladding layer 13 cannot be formed on the end face of the groove 12, as shown in FIG. It becomes a coating. Therefore, it is necessary to not stop rotating until the transparent material is completely cured by ultraviolet light.

Next, a translucent material with a high refractive index is filled into the groove of the base material 11 from one end using capillary action. The light-transmitting material with a high refractive index has a higher refractive index than the light-transmitting material forming the cladding layer 13, such as ultraviolet curing resin (trade name: Aronix M-210, Toagosei Chemical Industry Co., Ltd.). (manufactured by) is used. After filling the translucent material, it is cured by irradiation with ultraviolet rays, as shown in Fig. 1(c).
The core portion 14 is formed as shown in FIG.

Finally, a light-transmitting material with a low refractive index is applied to the surface of the base material 11 on which the core portion 14 is formed. As the light-transmitting material, the cladding layer 13
It is a substance that has a refractive index that is the same as or similar to the translucent material that formed the core. Application methods include spraying, spin coating, etc., and the thickness of the film is determined by the light beam propagating within the core. By irradiating the transparent material with ultraviolet rays and curing it, a cladding layer 15 is formed as shown in FIG. 1(d), and an optical waveguide is fabricated. I can do it.

[Effects of the Invention] As is clear from the above description, the present invention provides an optical waveguide in which stray light propagating within the cladding can be minimized (suppressed) and stray light detected as a signal can be minimized. can be provided, and the optical waveguide thereof can be easily manufactured.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the manufacturing process of the optical waveguide of the present invention, Figure 2 is a cross-sectional view showing the manufacturing process of a conventional optical waveguide, and Figure 3 is a state in which rotation is stopped during the process of spin-coding the groove. FIG. 3 is a cross-sectional view of a case where ultraviolet curing is performed. DESCRIPTION OF SYMBOLS 11... Base material, 12... Groove part, 13... Clad layer, 14. Core part, 15... Clad coating layer.

Claims (3)

[Claims] (1) A base material made of an opaque material having a groove, a cladding layer made of a translucent material with a low refractive index formed on the surface of the base material having the groove, and a high refractive index material filled in the groove of the cladding layer. 1. An optical waveguide comprising a core portion made of a light-transmitting material having a low refractive index, and a cladding layer made of a light-transmitting material having a low refractive index and covering the cladding layer and the upper portion of the core portion. (2) In the method for manufacturing an optical waveguide, a base material having a groove is formed of an opaque material, and a cladding layer is formed by applying a light-transmitting material with a low refractive index to the surface of the groove of the base material. Manufacture of an optical waveguide characterized by filling the grooves of the layer with a translucent material having a high refractive index to form a core portion, and forming a cladding layer thereon using a translucent material having a low refractive index. Method. (3) The method for manufacturing an optical waveguide according to claim 2, characterized in that a cladding layer is formed by applying a light-transmitting material with a low refractive index to the surface of the base material having the grooves by a spin coating method. .